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The cracking came in a protective layer that prevents scratches on the glass

Five tourists got out of the bay as fast as they could when they saw the lines in the coating

A protective coating on a glass sightseeing box that extends from the 103rd floor of the Willis Tower in Chicago cracked Wednesday night, but officials said no one was ever in danger.

Tourist Alejandro Garibay and four of his family members were standing in one of the glass boxes that jut out from the side of the tower when they heard a strange, worrisome noise below them.

"I looked down and I could see it cracking and lines going through the glass so we immediately just jumped off as fast as we could," Garibay told CNN affiliate WGN.

Photos:Scary viewing platforms

Photos:Scary viewing platforms

Willis Tower, Chicago – Visitors who step into one of the Ledge boxes at the Willis Tower in Chicago can see for 50 miles across four states. A protective coating on the glass cracked on Wednesday, May 28, but officials say visitors were never in danger. Click through this gallery to see more daring viewing platforms around the world:

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Photos:Scary viewing platforms

Dachstein Stairway to Nothingness, Austria – Visitors to the Dachstein Stairway to Nothingness must first cross Austria's highest bridge, which is 328 feet (100 meters) long and straddles a drop of 1,300 feet (396 meters). Then they face 14 steps that descend from the cliff face surrounded by glass walls.

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Photos:Scary viewing platforms

Alpspix Viewing Platform, Germany – The Alpspix Viewing Platform features two steel beams, both of which measure 79 feet (24 meters) in length. Visitors brave enough to walk to the end of the glass-walled platforms can look 3,281 feet (1,000 meters) down into the valley.

EdgeWalk CN Tower, Toronto – Located on the roof of the CN Tower's restaurant at a height of 1,168 feet (356 meters), the EdgeWalk in Toronto allows visitors to slip into climbing harnesses and walk around the edge of Canada's tallest structure. There's also a glass floor 1,122 feet (342 meters) above ground level.

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Cliffwalk, British Columbia – The Cliffwalk is a 700-foot (213-meter) walkway attached to a granite cliff face above the Capilano River in British Columbia. The highest point is 300 feet (90 meters) above the river.

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View from The Shard, London – The Shard in London is the tallest building in Western Europe. The View From the Shard is located on floors 68, 69 and 72. The best panoramas are from floor 72, at a height of 800 feet (244 meters). This open-air observation deck offers 360-degree views of the city.

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Stegastein lookout, Norway – The lookout, commissioned by the Norwegian Highway Department as part of a project to improve the appearance of the country's tourist routes, allows visitors to look straight down into the Aurlandsfjord, 2,000 feet (609 meters) below.

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Tokyo Skytree observation decks – The Tokyo Skytree is the world's third-tallest structure, with a height of 2,080 feet (634 meters), and has Japan's two highest observation decks.

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Top of Tyrol, Austria – The Top of Tyrol viewing platform looks over Austria's Stubai Glacier, providing visitors with spectacular views over 103 peaks.

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Dachstein Glacier Skywalk, Austria – The Dachstein Glacier actually comprises eight glaciers, and a visit to this high-altitude, glass-bottomed walkway is a great way to see them all.

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Trauttmansdorff Viewing Platform, Italy – The best views of Merano, Italy, are from this binocular-shaped viewing platform, high above a huge oak forest and the gardens of Trauttmansdorff Castle. The viewing platform is just one of several within the gardens.

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Grand Canyon Skywalk, Arizona – This steel and glass, horseshoe-shaped walkway extends 70 feet (21 meters) over the lip of the Grand Canyon, almost a mile above the valley floor. Apollo astronaut Buzz Aldrin was the first person to step onto the Skywalk, which cost $30 million.

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A Willis Tower spokesman Bill Utter clarified Thursday that it was a protective coating, not glass, that cracked -- as it sometimes does.

"At no time whatsoever was the integrity of the structure compromised," he said.

The ledges are designed to hold 5 tons, and the coating keeps the glass from being scratched.

"The protective layer did exactly what it was supposed to do," Utter said.

The four Skydeck ledges are a series of clear bays with glass floors that extend a little more than 4 feet from the building. Visitors can see the street 1,353 feet below their feet. According to the Skydeck website, each bay is made from three layers of half-inch thick glass.

Visitors who step into one of the boxes can see for 50 miles across four states.

Since 2009, 6 million people have ventured into the ledges, which retract into the tower when the windows need cleaning.

The ledges were closed for some time Thursday, but the Skydeck viewing area on the 103rd floor was open.

Around 7 p.m., Willis Tower's Facebook page indicated that "the new protective coating on Ledge 4 has been installed."

"Skydeck Chicago is open, including the other three unaffected Ledges, and Ledge 4 will be back open tomorrow," the post added alongside photos of workers at the scene.

The Hancock Building nearby has a new glass observation feature, but visitors hold on to handrails as the section tilts out about 1,000 feet above the city streets.